In general, the known embodiments of thrust-traction control cables used in the automobile industry comprise a sheathed steel cable both ends of which are provided with a terminal adapted to each specific case of application. Amongst the various types of control cable known in the art, a type commonly found is a control cable which links the gear-change mechanism with its operating shift lever. Essentially this comprises of a steel cable provided at both ends with corresponding terminals, and a sheath which partially covers the steel cable and has both ends attached to the respective fixed points of the vehicle structure provided along the route of the control cable, so that the control cable terminal corresponding to the shift-lever side, once coupled to that lever, forms an articulation which permits transmission of the thrust-traction forces applied on the operating shift lever. As an example of an articulation formed by coupling of the control cable with the shift lever there is the ball or ball-joint type, in which the control cable terminal comprises a ball-joint shell into which there fits with a tight fit a ball attached to a shift lever.
Once the control cable has been fitted on the vehicle, that is, once the control cable terminals have been coupled to the gear-change mechanism and to the shift lever and the ends of the steel cable sheath have been attached to corresponding fixed points, the sheathed portion of the steel cable has to be adjusted in order to achieve suitable functioning of the control cable by taking up the length tolerances which may be found on any particular vehicle.
In general, adjustment of the length of the sheathed portion of the steel cable of the control cable is implemented by means of an adjusting device fitted to one of the terminals of the control cable. The known embodiments of such adjusting devices essentially include a rod attached axially by one of its ends to the corresponding end of the steel cable, a housing on the terminal designed to receive the rod in such a way that the latter can slide in both directions, and means to fix the position of the rod with respect to the terminal once the length of the sheathed steel cable portion has been adjusted, which means essentially consist of a bolt which can be tightened down.
The known embodiments of adjusting devices such as those described above work in the way described below. The control cable is supplied ex-works with the rod of the adjusting device fixed to the terminal by means of said tighten-down bolt, and in such a way that the rod projects with respect to the terminal, that is, the control cable is supplied ex-works at its maximum length. Once the control cable has been fitted onto the vehicle, the length of the sheathed portion of the steel cable is adjusted by carrying out the following operations: first, the rod of the adjusting device must be released so that the rod can slide; a force is then applied manually to the rod in the direction corresponding to the direction of insertion of the rod into its housing on the terminal; and finally, keeping said force applied, the new position of the rod is fixed by means of the said tighten-down bolt.
The above-described functioning of the known embodiments of adjusting devices presents the following disadvantages. Firstly, adjustment of the length of the sheathed portion of the steel cable of the control cable is a function of the force applied manually on the rod, which leads to adjustments differing from one person to another or even according to the force applied in each case by one person. Secondly, the operations to fix the position of the rod, which are implemented by keeping a force applied manually on the rod, present difficulties which have an adverse effect on achieving the optimum degree of adjustment. Finally, another disadvantage is that the time needed to carry out the adjustment operation is relatively long and increases assembly costs.